Welcome to the forum !
Is there any way you could post us a photo please, it would help us to help you better.
Several thoughts come to mind here, sure lice is one, another would be ringworm [although if they have been outside during winter doubtful], they could just be shedding their winter coats, could be worms, could be any one of several possibilities.
'Ivermectin' or a similar product will clear lice and other 'bugs' but you really need to properly identify what the cause is first.
Wish I could be more help but apart from suggesting you call a vet not a lot else I can do without seeing them for myself.
Let us know how you go,